Explosion Venting

[dik]

I'm on a 'fast track' learning curve on something I know nothing about (yet).

I have a dielectric filled transformer in an enclosed space within an occupied industrial building. There are a lot of items that I have yet to determine, so pardon the ignorance.

I have yet to determine the 'kVA rating' of the transformer and the amount or type of 'mineral oil/dielectric' fluid and whether it is prone to exploding or what the effects of an 'short/arc' type of event (items that have a real impact on the answer).

If it's of any help, the size of the transformer is approx 8'x10'x12' and the size of the room it is in is approx 15'x20'x20'high.

I'm going over NFPA 69 this weekend and I'll be in contact with people that are familiar with explosion venting for this type of application next week.

Does anyone have an approx idea of the magnitude of the structure design pressures and the size of the 'blast panel'. I don't know if I'm looking at 20 psf, 50 psf, or 100 psf and I don't know if the panel is 2'x2' or 10'x10'.

I do know that portions of the existing structure will have to be reconstructed and some parts will have to be reinforced and that I require a 3 hour FRR, and some pressure resistant doors. I will likely have to vent this upwards and construct a 'doghouse' on the existing roof. The footprint of this should be small to minimise snow accumulation.

Dik

 

[SlideRuleEra]

dik - The electric generating station main power transformers that I have worked with are for outdoor installation, so explosion venting is not a concern. However, the adjacent blast walls are massive heavily reinforced concrete. You have a respectable sized transformer, especially considering the small room dimensions. The damage potential is significant, I would expect substantial structural upgrades and large vents to be needed. Since a transformer is almost entirely iron and copper, even dead weight will be surprisingly high.

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[dik]

The transformer is installed on the interior of the building and is about 60 years old. I have since learned that the dielectric oil is likely Voltesso 35. The volume of fluid is likely in the order of 3500 litres. The information is still contained on the transformer name plate, which I haven't seen yet. The transformer is massive constructed of heavy plate; I don't know the voltage or current, but it is used to power a couple of electric arc furnaces. It appears that the building was constructed around the transformers <G>, else I don't know how they placed them within the 3 wythe brick walls with 3'x6'10 door openings - maybe through the roof, but I couldn't tell.

The electrical code references the National Building Code and the main requirements for an interior dielectric filled transformer include ventilation to keep the temperature of the room less than 40degC and that it have explosion venting. The vault has to have a curb at least 4" high to contain oil. It is not feasible to replace the transformer with a dry system.

I was hoping that someone on the forum had encountered blast venting of transformers.

Dik